Finally happening but welcoming any good changes. Thank you for your work!
I do prefer that NSFW art stays though, hopefully there won't be a system that removes all the art that gets less than # of favs

aboutdata Just scrolling through this to see how the Alpha transition is going but I noticed nobody responded to your question. So to answer your question if nobody has already:
The '<3' is just a symbol that represents a heart. So to REALLY answer your question: It means "heart" in English.
Added 2019-03-03 22:13:04
I believe the goal in removing the NSFW wallpapers could cause the site to fall apart similar to the way tumblr has, but I mean, do what they will I suppose. One's personal perception of what is deemed NSFW or "porn" can vary greatly from person to person. Tan colored photos on that godforsaken site are being blurred out, blocked from search results or deleted altogether even if it's just a photo of a sand dune. All I'm saying is, I see problems in the future if that road is taken.